A teenage gunman caused a van travelling at more than 40mph to swerve and crash after he shot out the windscreen, police said today.

The driver was sprayed with shards of glass as he drove along, causing him to duck and cross into the path of traffic heading in the opposite direction.

Other drivers using the Newton Cap Viaduct outside Bishop Auckland, County Durham chased the gunman who was wearing camouflage gear, but he managed to escape.

Police investigating the incident shortly after 7.30am on Friday said it was lucky no-one was seriously injured.

The driver of the Fiat Dobolo van, a decorator, told police he saw the ginger-haired gunman deliberately point his air weapon at the van before he fired.

Pc Chris Luetchford (correct) said there was ''no logical explanation'' why the youth picked on the van, but the target was ''clearly selected.'' ''It was a stupid thing to do and could quite easily have caused a crash and it was fortunate indeed that no-one was hurt,'' he said. Police want to trace the drivers of a VW Golf and a blue Rover who chased the teenager and anyone else who witnessed the shooting.